Hi,
I exactly had the same issue last week and I followed below steps:
To resolve this issue:
Remove the Azure AD account (owner) from all admin roles.
Hard delete the quarantined object in the cloud. This is your duplicate account in Azure Adminxxxx.domain.com
Do a delta sync
The next sync cycle will take care of soft-matching the on-premises user to the cloud account because the cloud user is now no longer a global admin.
Restore the role memberships for the owner.
Wait for few hours or atleast 12 hours to get it corrected in Azure.
It is not straight away as far as I have noticed.
Hope this helps.
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